NASA.

GSS CO2 sensors used on International Space Station

Few people are aware of the effects of elevated levels of CO2. The normal level of CO2 is around 400 parts per million (ppm). In a closed room with several people inside, this can rapidly rise to 2,000 ppm. The stuffy feeling making people yawn is, in fact, not the lack of ‘fresh air’ or oxygen, but your body reacting to high levels of CO2. At higher levels, it becomes harder to concentrate with narcotic-like symptoms as levels rise further.

There can be few places where the impact of elevated CO2 levels is more important than in a spacecraft. Such increases can impinge on the crew’s ability to correctly carry out their duties. NASA has released details of research that it has been doing on the effects of CO2 levels in the International Space Station (ISS), which can be found at https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20150019624.pdf entitled “CO2 on the International Space Station: An Operations Update”.

NASA has found that crew members develop CO2 related symptoms at lower CO2 levels than would be expected terrestrially. Since 2010, operational limits have been controlled to an average of 4.0 mm Hg or below as driven by crew symptomatology. However, crew members have reported symptoms starting as low as 2.3 mm Hg that are due to CO2. Between 2.3-2.7 mm Hg, fatigue and full headedness were reported. Between 2.7 and 3.0 mm Hg, errors occurred in procedures. And above 3.0-3.4 mm Hg, headaches were reported. It was also noted that crew members varied in their sensitivity to CO2 levels. This evidence indicated to NASA that an operational level of between 0.5 and 2.0 mm Hg may maintain health and performance, which they want to research further.

CO2 sensors from Gas Sensing Solutions were selected because they use proprietary, mid range, infrared LEDs that only use a tiny amount of power, giving a long operational life from a battery. Supported by GSS distributor, SST Sensing, NASA designed and made personal CO2 monitors using GSS ExplorIR® sensors,which were used on the ISS to gather data. More information can be found at:

Calum MacGregor, GSS CEO, said, “A closed system is the best way to monitor the effects of changing a variable such as CO2 levels. The ISS is a perfect example of a closed system and has given some very interesting results of the real effects of CO2 levels on alertness and health. Hard data from NASA on the harmful effects of elevated CO2 levels will help raise the level of awareness of this issue. Following the success of this rugged, wide range CO2 monitor, we have had several enquiries from other companies wanting to use our battery powered CO2 sensors to make personal monitors for a variety of applications where people could be exposed to high levels of CO2. Also, many industries require their workers to enter enclosed spaces such as pub cellars, mines, submarines and tunnels, where environmental monitoring is critical to safety and a personal CO2 monitor with an alarm could save lives.”

GSS technology

CO2 sensors work by measuring how much light is absorbed by CO2 molecules in the 4.2 and 4.4 microns range as it passes through the sample gases, which is called Non-Dispersive Infrared (NDIR) absorption. The amount of absorption indicates how much CO2 is present. GSS developed proprietary LEDs that are specifically tuned to emit at these wavelengths. The LEDs use very little power and turn on almost instantly, enabling sensor readings to be made in less than a second. As a result, GSS has pioneered the development of CO2 sensors that can be powered by batteries for long periods of up to ten years. Competitor sensors use IR sources that require significantly more power per measurement and also take much longer to reach a stable condition for a measurement, resulting in the need for mains power.

Gas Sensing Solutions (GSS) www.gassensing.co.uk

GSS is a world leader in CO2 sensor design, manufacture and customisation. Its disruptive technology uses proprietary, mid range, infrared LED sensors to enable best-in-class records for fastest response times, lowest power consumption and longest product lifetime. Based in Scotland, this technology pioneer exports state-of-the-art sensors worldwide, and has in-house bespoke development capabilities to support its international customer base. Tel: +44 1236 781900 info@gassensing.co.uk